This invention relates to an improved coupling between a drive mechanism and the mixing drum of a concrete mixer. More particularly, the present invention relates to an auxiliary drive and bearing apparatus with means for selectively disengaging the transmission from the mixing drum to allow the drum to freewheel about the axis of rotation in the event of a failure of the transmission.
Concrete mixing drums are well known in the art. Generally, they comprise a drive mechanism which rotates a large mixing drum. Usually mixing drums are tilted so that the major portion of the weight of the drum is borne by the lower mounting. The drive means for rotating a drum is generally connected to the drum at this same end.
A long-standing problem in the redi-mix industry arises when the drive mechanism on the rotating mixing drum of a concrete mixer fails or malfunctions. It is not uncommon for the drive or bearing mechanism to fail causing the mixing drum to stop rotating. This problem is further compounded if the mixing drum was loaded with concrete when the malfunction occurs. The costs associated with rehabilitating a mixing drum that has several yards of concrete hardened in its interior are relatively high.
Auxiliary or secondary drive mechanisms for concrete mixers have been proposed as a way to avoid this problem. Upon failure of the primary drive mechanism, an auxiliary drive mechanism can be engaged to rotate the mixing drum. See, for example, U.S. Pat. No. 4,097,925 to Butler, Jr. and U.S. Pat. No. 3,136,165 to Pitts. However, in conventional drive mechanisms, a failure of the primary bearings or drive mechanism will often lock the mixing drum in a stationary position, and then the mixing drum cannot be rotated even with an auxiliary drive mechanism. An auxiliary bearing and drive mechanism that permits rotation of the mixing drum regardless of the type of primary bearing or drive mechanism failure would be a substantial improvement over conventional drive mechanisms.
One object of this invention is to provide a secondary or backup bearing arrangement located between the primary drive and the mixing drum of the cement mixer to allow rotation of the mixing drum if the primary drive mechanism or bearings fail.
Another object of the invention is to provide secondary bearing coupling means for selectively disengaging the primary drive from the mixing drum so the mixing drum can freewheel about the axis of rotation in the event of a primary drive failure which would otherwise prevent the mixing drum from rotating.
Another object of the invention is to provide an auxiliary drive mechanism for engaging and rotating the concrete mixer mixing drum once the bearing coupling means has been disengaged.
According to the present invention, a drive and bearing arrangement for a rotatable member, such as a concrete mixing drum or the like, comprises first and second drive means for providing drive forces to the rotatable member, and first and second bearing means for rotatably supporting an end of the rotatable member. The first bearing means is coupled to the first drive means and the rotatable member. The second bearing means selectively and alternatively supports the end of the rotatable member and is coupled to the rotatable member and to the first bearing means.
The second bearing means can be selectively decoupled from the first bearing means to allow the second bearing means to alternatively support the end of the rotatable member. The decoupling means includes a removable locking element formed to selectively couple the second bearing means to the first bearing means.
According to one aspect of the invention, the second bearing means includes a first element coupled to the first drive means and a second element coupled to the rotatable member. The first element includes a first flange member and a first cylindrical member extending from the first flange member. The second element includes a second flange member and a second cylindrical member extending from the second flange member. The first and second cylindrical members are formed to engage and concentrically rotate relative to one another.
According to another aspect of the invention, the second bearing means includes a removable locking element for selectively coupling the first flange member to the second flange member. Removal of the locking element decouples the first flange member from the second flange member and allows the second flange member to rotate relative to the first flange member.
In one embodiment, the first and second flange members are formed to include a plurality of notches. The second bearing means includes a locking ring formed to include a plurality of notch engaging projections for engaging the notches to prevent relative movement between the first and second flanges.
In another embodiment, the first and second flange members are formed to include a plurality of apertures. The second bearing means includes a plurality of locking bolts for engaging the apertures to prevent relative movement between the first and second flanges.
According to another aspect of the invention, bearing elements are disposed between the first and second cylindrical members. These bearing elements reduce friction when the second bearing means is alternatively supporting the end of the rotatable member.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.